Foamed, opacifying elements with thermally transferred images

ABSTRACT

A foamed, opacifying element has a thermal colorant image on either an opposing external surface and an internal surface of a porous substrate. The internal surface has a dry foamed composition disposed thereon as a dry opacifying layer that comprises: (a) 0.1-40 weight % of porous particles; (b) at least 10 weight % of an at least partially cured binder material; (c) at least 0.2 weight % of one or more additives comprising a surfactant; (d) less than 5 weight % of water; and (e) at least 0.002 weight % of an opacifying colorant different from all of the one or more (c) additives, which opacifying colorant absorbs predetermined electromagnetic radiation. The thermal colorant image is derived from thermal colorant transfer of sublimable colorants from a thermal donor element.

RELATED APPLICATIONS

Reference is made to the following copending and commonly assignedpatent applications:

U.S. Ser. No. 15/______ (filed on even date herewith by Herrick andNair), and entitled “Method for Preparing Thermally Imaged OpacifyingElements” (Attorney Docket K002167/JLT);

U.S. Ser. No. 14/181,766 (filed Feb. 17, 2014 by Lofftus, Nair, andBrick), now published as U.S. Patent Application Publication2015/0234098;

U.S. Ser. No. 15/144,893 (filed May 3, 2016 by Brick, Nair, and McHugh)that is a continuation-in-part of commonly assigned U.S. Ser. No.14/730,280, filed Jun. 4, 2015 by Brick, Nair, Lindner, and Pyszczek,now abandoned.

U.S. Ser. No. 15/144,875 (filed May 3, 2016 by Nair, Brick, andPyszczek), recently allowed, that is a continuation-in-part of commonlyassigned U.S. Ser. No. 14/730,269, filed Jun. 4, 2015 by Brick, Nair,Lindner, and Pyszczek, now abandoned;

U.S. Ser. No. 15/144,911 (filed May 3, 2016 by Brick, Nair, Lindner, andBessey) that is also a continuation-in-part of commonly assigned U.S.Ser. No. 14/730,280, filed Jun. 4, 2015 by Brick, Nair, Lindner, andPyszczek, now abandoned;

U.S. Ser. No. 15/239,915 (filed Aug. 18, 2016 by Nair, Brick, andPyszczek);

U.S. Ser. No. 15/239,978 (filed Aug. 18, 2016 by Nair, Brick, andSedita); and

U.S. Ser. No. 15/239,938 (filed Aug. 18, 2016 by Nair, Brick, andBessey);

the disclosures of all of which applications are incorporated herein byreference.

FIELD OF THE INVENTION

This invention relates to foamed, opacifying elements that can be usedas light-blocking (blackout) articles, which foamed, opacifying elementsalso have colorant images provided by thermal transfer processes. Thefoamed, opacifying elements have a dry opacifying layer derived fromfoamable aqueous compositions that include unique porous particles in amixture with other essential components so that composition foaming,application to a porous substrate, drying, and densifying can be readilyaccomplished.

BACKGROUND OF THE INVENTION

Draperies are primarily designed for style and appearance, and aregenerally made from fabrics of various colors which are printed or insome other way carry a design or image. Digital printing is replacingtraditional methods in the textile industry. The main drivers are thecost-efficiency, ability to personalize prints and flexibility.Traditional screen-printing is being replaced by digital textileprinting solutions like thermal transfer or sublimation printing forshorter production runs and personalized prints that require multiplecolors and detailed images. Thermal transfer or heat transfer printingis a method to impart a desired color or color pattern or image to asynthetic fabric such as polyester, nylon and acrylic. Thermal transferprinting uses thermally responsive inks containing sublimable colorantsthat under the influence of heat sublime or vaporize onto the surface ofthe fabric. penetrate the fibers and be entrained therein or attach tothe textile fiber. Heat transfer printing processes and materials arequite old and described in numerous publications, for example, U.S. Pat.No. 3,363,557 (Blake), U.S. Pat. No. 3,952,131 (Sideman), U.S. Pat. No.4,139,343 (Steiner), U.S. Pat. No. 6,036,808 (Shaw-Klein et al.), U.S.Pat. No. 8,628.185 (Hale et al.), U.S. Pat. No. 9,315,682 (Delys etal.,), U.S. Pat. No. 4,117,699 (Renaut), U.S. Pat. No. 4,097,230(Sandhu), U.S. Pat. No. 4,576,610 (Donenfeld), U.S. Pat. No. 5,668,081(Simpson et al.), and U.S. Pat. No. 7,153,626 (Foster et al.).

In accordance with such imaging technology, a color pattern(discontinuous or image) to be imparted to a fabric substrate such as awoven, unwoven, or knitted material, is preprinted on a substrate(usually paper or a sheet of non-textile material) referred to as thetransfer sheet or transfer donor element. as a print or image with anink that contains the sublimable colorant. The inks used for preparingthe printed pattern contain colorants that are selected to sublime at atemperature that does not compromise the integrity of the fabric ortextile substrate. The inks can be applied to an inert, transfer donorsupport, conventionally paper, by any number of printing processes knownin the art, including gravure, flexography, flat screen, rotary screen,electrophotography, and ink jet printing. The preprinted transfer donorelement and the fabric to be printed are brought into contact undercontrolled conditions of time, temperature and pressure such that thecolorant of the image is sublimed and transferred from the transferdonor element to the fabric substrate that must be of such a nature thatit will receive and retain the transferred inks, to provide a permanentprint or image thereon. Since the colorant becomes part of the structureof the material, the images on the fabric are vivid, resistant to fadingor deteriorating after multiple washings and show good crock resistance.In addition, the fabric substrate must be resilient to the heat andpressure required for image transfer from volatilization or sublimationof the respective inks that are condensed on and are absorbed by atleast the outer surface layers of the individual fibers of the fabricsubstrate. This effect can readily be obtained on many fabrics made fromsynthetic fibers, especially polyester fibers and polyester blends withnatural fibers.

For example, U.S. Pat. No. 4,139,343 (noted above) discloses transfersheets for heat transfer printing polyester textiles in yellow hues,inks that are useful in making such transfer sheets, an improved processfor heat transfer printing polyester textiles and the printed or dyedfabrics thereby produced.

The art has recognized the difficulty of transferring images to fabricsmade from either naturally-occurring or synthetic fibers, particularlyfabrics comprising cotton, as described for example in U.S. Pat. No.4,576,610 (noted above), in which a sublimable composition is formulatedwith a polyester bonding resin in which the polymer has a substantialamount of free carboxyl groups to markedly improve the depth, evennessand fastness of colors imparted by sublimation dye techniques to cottonand other naturally-occurring fibrous materials.

Draperies made from fabrics and printed as described above to create adesired visual effect are generally ineffective for preventing asubstantial quantity of light penetration into a room from outsidesources resulting in a corresponding undesirable level of illuminationwhere light is not needed. To completely block undesired light,draperies generally consist of two separate elements: a decorative orprinted face fabric, and a separate blackout material (or liner)attached to the decorative face fabric by sewing or other means. Theblackout material or liner is typically turned towards a window or otherlight source in front of which the decorative face fabric hangs.

“Blackout” or light-blocking materials typically refer to articles thatare substantially impermeable to light such as visible or UV radiation.When a blackout material is used to cover a window or other openingthrough which light can pass, it is designed to completely block out allexternal light from entering the room through that window or opening.

Blackout materials are desired by hotels and residences to ensure anideal sleep environment, to protect the interior from ultraviolet lightdamage, and to provide privacy. Residential use of blackout materials isalso desirable for those living in densely populated urban or suburbanareas where the amount of light penetration into a window at night maybe considerable due to sources such as street lights, light fromadjacent buildings, and vehicle headlights. Hospitals may also use suchmaterials to promote privacy and comfort for patients especially wheremultiple patients share the same areas.

Costs to fabricate light-blocking draperies (lined with a blackoutmaterial) are higher, compared to that of single-textile or unlineddraperies, due to added expense of creating a blackout liner materialand labor for attaching the blackout liner material to the face fabric.In addition, drapery fabricators must keep sufficient inventory ofblackout liner material on hand. U.S. Pat. No. 5,741,582 (Leaderman etal.), suggests the possibility of imprinting, dyeing, or decorating ablackout architecture made up of material fabric on both sides of thedrapery lining instead of the exposed foam thereby serving as aself-lined drapery fabric.

Blackout materials or liners are multi-layer structures, with a minimumof three separate coated layers. For example, U.S. Pat. No. 4,677,016(Ferziger et al.) describes a light-blocking article comprising a fabricbacked with a first coat of white acrylic foam, followed by a secondcoat of an acrylic foam having an opaque color, and finally, a thirdcoat of white acrylic foam. U.S. Patent Application Publication2002/0122949 (Richards), describes a light-blocking article as alaminated structure comprised of two layers of fabric, two layers offoam, and a metallized plastic sheet.

These multi-layer blackout liners are sufficiently impermeable to lightbut unsuitable for thermal transfer printing. They are prone tosubstantial off-gassing thereby producing unacceptable levels of noxiousfumes at the temperatures required to sublime and transfer sublimablecolorants. High temperatures may also cause multi-layer blackoutmaterials to suffer delamination or loss of adhesion between layers.Poor image quality due to incomplete and inconsistent transfer of thesublimable inks from donor elements to multi-layer blackout liners iscommonly reported. Such problems can arise with multi-layer blackoutliners known in the art even those that comprise polyester or anothersynthetic fabric including a blend, because of the continuous layer ofsandwiched carbon black that can absorb heat and thereby act as a heatsink during the intended sublimation process. These unwanted effectscould arise in metallized blackout curtains as well.

Thus, there is a need to provide blackout articles containing suitablecolorant images or prints achieved using thermal transfer chemistriesand processes that avoid these problems.

SUMMARY OF THE INVENTION

The present invention provides a foamed, opacifying element comprising athermal colorant image, the foamed, opacifying element furthercomprising a porous substrate having an opposing external surface and aninternal surface, the internal surface having a dry foamed compositiondisposed thereon as a dry opacifying layer,

wherein the dry foamed composition comprises:

(a) at least 0.1 weight % and up to and including 40 weight % of porousparticles, each porous particle comprising a continuous polymeric phaseand a first set of discrete pores dispersed within the continuouspolymeric phase, the porous particles having a mode particle size of atleast 2 μm and up to and including 50 μm and a porosity of at least 20volume % and up to and including 70 volume %, and the continuouspolymeric phase having a glass transition temperature greater than 80°C. and comprising a polymer having a viscosity of at least 80centipoises and up to and including 500 centipoises at a shear rate of100 sec⁻¹ in ethyl acetate at a concentration of 20 weight % at 25° C.;

(b) at least 10 weight % of an at least partially cured binder material;

(c) at least 0.2 weight % of one or more additives comprising asurfactant;

(d) less than 5 weight % of water; and

(e) at least 0.002 weight % of an opacifying colorant different from allof the one or more (c) additives, which opacifying colorant absorbspredetermined electromagnetic radiation,

all amounts being based on the total weight of the dry foamedcomposition,

wherein the dry opacifying layer has a light blocking value of at least4 as well as a luminous reflectance that is greater than 40% as measuredby the Y tristimulus value, and

wherein the thermal colorant image is disposed on the opposing externalsurface, the dry opacifying layer, or both the opposing external surfaceand the dry opacifying layer.

The foamed, opacifying elements and methods used to prepare themaccording to the present invention provide a number of advantages. Thepresent invention overcomes the disadvantages of the articles known inthe art by providing stand-alone, self-lined draperies (foamed,opacifying elements) that are impermeable to light and durable enough towithstand the temperatures required for thermal transfer printingoperations. The inventive foamed, opacifying element is a stand-alone,self-lined, light-blocking drapery having a porous substrate, a singledry opacifying layer derived from a dry foamed composition disposed onone supporting side (or internal surface) of the porous substrate, and athermally transferred colorant image disposed on the opposing externalsurface porous substrate or the dry opacifying layer. In mostembodiments, the foamed, opacifying elements consist only of thesespecific features. Thus, either or both opposing external surface andinternal surface (or opposing sides) of the foamed, opacifying elementcan have an applied decorative pattern or image provided using thermaltransfer processes.

The foamed, opacifying element provided according to the presentinvention avoids the use of a layer of carbon black that can act as aheat sink during thermal colorant transfer processes. In addition, thepresent invention reduces the effluence of noxious fumes common duringknown transfer colorant transfer processes.

The foamed, opacifying elements contain very low amounts of opacifyingcolorants in the dry opacifying compositions that are not damaged bytemperatures greater than 100° C. that may be used during the thermalcolorant transfer processes or during manufacturing drying operations.The foamed, opacifying elements (or light-blocking articles) such asstand-alone, self-lined blackout draperies exhibit desired opacity,improved flexibility, “hand,” and drapeability. Manufacturing operations(methods) can be readily carried out in a continuous manner for example,in a roll-to-roll operation.

It is highly important to understand that the foamed, opacifyingelements according to this invention have simpler construction thanlight-blocking articles described in the prior art. For example, sucharticles comprise a single dry opacifying layer that is both opacifyingand resistant to delamination at high temperature and pressure. Thepresent invention avoids thick and multi-layer constructions whileproviding the noted advantages with very little opacifying colorant (forexample, up to and including 1 weight % of total solids). Because theopacifying colorant can be contained within the porous particles andthere is so little of the opacifying colorant used, the foamed,opacifying element remains light-colored and when it is damaged orpunctured, the escape of opacifying colorant and its effect on othermaterials are minimized. Additionally, the low levels of opacifyingcolorant enables more efficient thermal colorant transfer.

In some embodiments, the foamed, opacifying elements prepared accordingto the present invention comprise a single dry opacifying layer thatalso has any or all antimicrobial, opacifying, and flame retardantproperties as well as the required light-blocking properties.

DETAILED DESCRIPTION OF THE INVENTION

The following discussion is directed to various embodiments of thepresent invention and while some embodiments can be desirable forspecific uses, the disclosed embodiments should not be interpreted orotherwise considered to limit the scope of the present invention, asclaimed below. In addition, one skilled in the art will understand thatthe following disclosure has broader application than is explicitlydescribed and the discussion of any embodiment.

Definitions

As used herein to define various components of the foamed aqueouscomposition, foamable aqueous composition, dry foamed composition,thermal colorant transfer compositions, or materials used to prepare theporous particles, unless otherwise indicated, the singular forms “a,”“an,” and “the” are intended to include one or more of the components(that is, including plurality referents).

Each term that is not explicitly defined in the present application isto be understood to have a meaning that is commonly accepted by thoseskilled in the art. If the construction of a term would render itmeaningless or essentially meaningless in its context, the termdefinition should be taken from a standard dictionary.

The use of numerical values in the various ranges specified herein,unless otherwise expressly indicated otherwise, are considered asapproximations as though the minimum and maximum values within thestated ranges were both preceded by the word “about.” In this manner,slight variations above and below the stated ranges can be used toachieve substantially the same results as the values within the ranges.In addition, the disclosure of these ranges is intended as a continuousrange including every value between the minimum and maximum values.

Unless otherwise indicated, the terms “foamed, opacifying element,”“light-blocking element,” “light-blocking article,” and “light-blockingdrapery” are intended to refer to the same material.

Unless otherwise indicated, the term “opposing external surface” refersto a planar surface of a porous substrate (defined below) that typicallydoes not have a dry opacifying layer disposed thereon. Such opposingexternal surface can be the surface of the foamed, opacifying elementthat typically faces a viewer.

Unless otherwise indicated, the term “internal surface” refers to aplanar surface of a porous substrate (defined below) on which a dryopacifying layer is disposed for blocking impinging light from varioussources such as sunlight, street light, and any source of external lightthat is to be blocked from exiting the foamed, opacifying element'sopposing external surface traveling through the dry opacifying layer.

The terms “porous particle” and “porous particles” are used herein,unless otherwise indicated, to refer to porous organic polymericmaterials useful in the foamable aqueous compositions, foamed aqueouscompositions, dry foamed compositions, and foamed, opacifying elements.The porous particles generally comprise a solid continuous polymericphase having an external particle surface and discrete pores dispersedwithin the continuous polymeric phase. The continuous polymeric phasealso can be chemically crosslinked or elastomeric in nature, or bothchemically crosslinked and elastomeric in nature.

The continuous polymeric phase of the porous particles generally has thesame composition throughout that solid phase. That is, the continuouspolymeric phase is generally uniform in composition including anyadditives (for example, colorants) that can be incorporated therein. Inaddition, if mixtures of polymers are used in the continuous polymericphase, generally those mixtures also are dispersed uniformly throughout.

As used in this disclosure, the term “isolated from each other” refersto the different (distinct) pores of same or different sizes that areseparated from each other by some of the continuous polymeric phase, andsuch pores are not generally interconnected.

The terms “first discrete pore” and “second discrete pore” refer todistinct sets of isolated pores in the porous particles useful in thepresent invention. These first and second discrete pores refer todistinct sets of pores. Each distinct set of pores includes a pluralityof pores that are isolated from each other, and the pores of each set ofpores are isolated from all other pores of the other sets of pores inthe porous particle. Each set of pores can have the same mode averagesize or both sets can have the same mode average size. The word“discrete” is also used to define different droplets of the first andsecond aqueous phases when they are suspended in the oil (solvent) phaseused for making the porous particles.

The porous particles can include “micro,” “meso,” and “macro” discretepores that, according to the International Union of Pure and AppliedChemistry, are the classifications recommended for discrete pore sizesof less than 2 nm, from 2 nm to 50 nm, and greater than 50 nm,respectively. Thus, while the porous particles can include closeddiscrete pores of all sizes and shapes (that is, discrete pores entirelywithin the continuous polymeric phase) providing a suitable volume ineach discrete pore, macro discrete pores are particularly useful. Whilethere can be open macro pores on the surface of the porous particle,such open pores are not desirable and may be present only by accident.The size of the porous particle, the formulation, and manufacturingconditions are the primary controlling factors for discrete pore size.However, typically the discrete pores independently have an average sizeof at least 100 nm and up to and including 7,000 nm, or more likely atleast 200 nm and up to and including 2,000 nm. Whatever the size of thediscrete pores, they are generally distributed randomly throughout thecontinuous polymeric phase. If desired, the discrete pores can begrouped predominantly in one part (for example, “core” or “shell”) ofthe porous particles.

In some embodiments, where there are different sets of discrete pores,the discrete pores of a first set are predominantly nearer then externalparticle surface compared to the discrete pores of a second set. Forexample, a set of smaller discrete pores can be predominantly close tothe external particle surface compared to a set of larger discretepores. As used herein, the term “predominant” means that a larger numberfraction of pores of one size is found in a “shell” area nearer thesurface of the porous particle than one would expect based on the totalnumber fraction of the two or more types (sizes) of pores present in theporous particle.

The porous particles used in this invention generally have a porosity ofat least 20 volume % and up to and including 70 volume %, or likely atleast 40 volume % and up to and including 65 volume %, or more typicallyat least 45 volume % and up to an including 60 volume %, all based onthe total porous particle volume. Porosity can be measured using amercury intrusion technique where mercury crushes the closed pores athigh pressure and the volume of (irreversibly) crushed pores is used tomeasure porosity (pore volume). A high degree of separation in pressureis observed between the interstitial filling of mercury between theparticles and pore crushing. The interstitial filling is a function ofboth particle size distribution and particle packing in thepenetrometer, while the pore crushing signal is due to thecompressibility of the particles as a function of wall thickness andvariations in its modulus.

“Opacity” is a measured parameter of a foamed, opacifying element thatcharacterizes the extent of transmission of electromagnetic radiationsuch as visible light. A greater opacity indicates a more efficientblocking (hiding) of predetermined radiation (as described below). Inthe present invention, the “opacity” of a foamed, opacifying element canbe measured as the light-blocking value (LBV), as described below withthe Examples, which determines the extent to which the impingingradiation or light is blocked by the foamed, opacifying element. Thehigher the LBV, the greater the light-blocking ability exhibited by thefoamed, opacifying element. The articles of the present inventiongenerally exhibit a LBV of at least 4.

Glass transition temperatures of the organic polymers used to preparethe continuous polymeric phase can be measured using DifferentialScanning calorimetry (DSC) using known procedures. For many commerciallyavailable organic polymers, the glass transition temperatures are knownfrom the suppliers.

Polymer viscosity (in centipoises) for the continuous polymeric phasecan be measured in ethyl acetate at a concentration of 20 weight % ofthe polymer at 25° C. in an Anton Parr MCR 301 stress rheometer in acoquette using steady shear sweeps. Shear rate at 100 sec⁻¹ wascalculated from the resulting graphical plot of viscosity vs. shearrate.

CIELAB L*, a*, and b* values have the known definitions according to CIE1976 color space or later known versions of color space and werecalculated assuming a standard D65 illuminant. The Y tristimulus valueof the X, Y, and Z tristimulus values can be used as a measure of theluminous reflectance or “brightness” of a dry opacifying layer.

Unless otherwise indicated, the terms “thermal transfer process” and“heat transfer process” are intended to refer to the same sublimation orvapor-phase process of printing or dyeing textile fabrics whereintextiles are colored with thermal colorants that undergo sublimation attemperatures below that at which the physical integrity of the textileis impaired.

Uses

The foamable aqueous compositions and foamed aqueous compositions can beused to prepare foamed, opacifying elements that in turn can be used asradiation (light) blocking materials in the form of blackout liners,roller shades, privacy curtains, banners, and window shades forairplanes, hospitals, homes, labels, projection screens, textilefabrics, and packaging materials. The foamed, opacifying elements canalso exhibit improved sound and heat blocking properties, and can havesuitable images provides by thermal colorant transfer processes asdescribed below for viewing on one or both sides. The term “blackoutliner” is intended to include but not limited to, window curtains,shades for all purposes, draperies, room dividers, privacy curtains, andcubicle curtains suitable for various environments and structures.

Foamable Aqueous Compositions

The foamable aqueous compositions designed for use in the presentinvention can be suitably aerated to provide foamed aqueous compositionsto prepare a foamed, opacifying element according to the presentinvention. In many embodiments, the foamable aqueous compositions havethe following five essential components that are the only componentsneeded to obtain the light-blocking properties and advantages describedabove: (a) porous particles as described below; (b) a binder material,also described below; (c) one or more additives as described below,comprising at least one surfactant; (d) water; and (e) an opacifyingcolorant different from all of the compounds of component (c), whichopacifying colorant absorbs “predetermined electromagnetic radiation”(generally UV to near-IR, for example, absorbing the radiation of allwavelengths of from 350 nm to 800 nm or from 350 nm to and including 700nm). Optional (non-essential) components that can be included are alsodescribed below.

The foamable aqueous composition generally has at least 35% and up toand including 70% solids, or more particularly at least 40% and up toand including 60% solids.

Porous Particles:

Porous particles used in the present invention containing discrete pores(or compartments) are used in the dry opacifying layers and they aregenerally prepared, as described below, using one or more water-in-oilemulsions in combination with an aqueous suspension process, such as inthe Evaporative Limited Coalescence (ELC) process. The details for thepreparation of the porous particles are provided, for example, in U.S.Pat. No. 8,110,628 (Nair et al.), U.S. Pat. No. 8,703,834 (Nair), U.S.Pat. No. 7,754,409 (Nair et al.), U.S. Pat. No. 7,887,984 (Nair et al.),U.S. Pat. No. 8,329,783 (Nair et al.), and U.S. Pat. No. 8,252,414(Putnam et al.), the disclosures of all of which are hereby incorporatedherein by reference. The porous particles are generally polymeric andorganic in nature (that is, the continuous polymeric phase is polymericand organic in nature) and non-porous particles (having less than 5%porosity) are excluded. Inorganic particles can be present on the outersurface as noted below.

The porous particles are composed of a continuous polymeric phasederived from one or more organic polymers that are chosen so that thecontinuous polymeric phase has a glass transition temperature (T_(g))greater than 80° C., or more typically at least 100° C. and up to andincluding 180° C., or more likely at least 110° C. and up to andincluding 170° C. as determined using Differential Scanning calorimetry.Polymers having a T_(g) greater than 200° C. are typically less usefulin the continuous polymeric phase.

In addition, the continuous polymeric phase comprises one or morepolymers each of which has a viscosity of at least 80 centipoises (0.080mPa sec) and up to and including 500 centipoises (0.5 mPa sec) at ashear rate of 100 sec⁻¹ as measured in ethyl acetate at a concentrationof 20 weight % at 25° C. This feature is important to optimize thepreparation of porous particles used in the practice of this inventionso that the prepared porous particles have a narrow particle sizedistributions and high porosity.

For example, the continuous polymeric phase can comprise one or morepolymers having the properties noted above, wherein generally at least70 weight % and up to and including 100 weight % based on the totalpolymer weight in the continuous polymeric phase, is composed of one ormore cellulose polymers (or cellulosic polymers) including but notlimited to, those cellulosic polymers derived from one or more ofcellulose acetate, cellulose butyrate, cellulose acetate butyrate, andcellulose acetate propionate. A polymer derived solely from celluloseacetate butyrate is particularly useful. Mixtures of these cellulosepolymers can also be used if desired, and mixtures comprising a polymerderived from cellulose acetate butyrate as at least 80 weight % of thetotal of cellulose polymers (or of all polymers in the continuouspolymeric phase) are particularly useful mixtures.

In general, the porous particles used in the present invention have amode particle size equal to or less than 50 μm, or of at least 2 μm andup to and including 50 μm, or typically of at least 3 μm and up to andincluding 30 μm or even up to and including 40 μm. Most useful porousparticles have a mode particle size of at least 3 μm and up to andincluding 20 μm. Mode particle size represents the most frequentlyoccurring diameter for spherical particles and the most frequentlyoccurring largest diameter for the non-spherical particles in a particlesize distribution histogram.

Pore stabilizing materials such as hydrocolloids can be present withinat least part of the volume of the discrete pores distributed throughoutthe continuous polymeric phase, which pore stabilizing materials aredescribed in patents cited above. In some embodiments, the same porestabilizing material is incorporated in essentially all discrete poresthroughout the entire porous particles. In many embodiments, the porestabilizing hydrocolloids are selected from the group consisting ofcarboxymethyl cellulose (CMC), a gelatin, a protein or proteinderivative, polyvinyl alcohol and its derivatives, a hydrophilicsynthetic polymer, and a water-soluble microgel.

It can be desired in some embodiments to provide additional stability ofone or more discrete pores in the porous particles during theirformation, by having one or more amphiphilic block copolymers disposedat the interface of the one or more discrete pores and the continuouspolymeric phase. Such materials are “low HLB,” meaning that they have anHLB (hydrophilic-lipophilic balance) value as it is calculated usingknown science, of 6 or less, or even 5 or less. The details of theseamphiphilic polymers and their use in the preparation of the porousparticles are provided in U.S. Pat. No. 9,029,431 (Nair et al.), thedisclosure of which is hereby incorporated herein by reference.

A particularly useful amphiphilic block copolymer useful in suchembodiments comprises poly(ethyleneoxide) and poly(caprolactone) thatcan be represented as PEO-b-PCL. Amphiphilic block copolymers, graftcopolymers and random graft copolymers containing similar components arealso useful.

Such an amphiphilic block copolymer can be generally present in theporous particles in an amount of at least 1 weight % and up to andincluding 99.5 weight %, or at least 2 weight % and up to and including50 weight %, based on total porous particle dry weight.

The porous particles used in this invention can be spherical ornon-spherical depending upon the desired use. In a method used toprepare the porous particles, additives (shape control agents) can beincorporated into the first or second aqueous phases, or in the oil(organic) phase to modify the shape, aspect ratio, or morphology of theporous particles. The shape control agents can be added prior to orafter forming the water-in-oil-in-water emulsion. In either case, theinterface at the oil and second water phase is modified before organicsolvent is removed, resulting in a reduction in sphericity of the porousparticles. The porous particles used in the present invention can alsocomprise surface stabilizing agents, such as colloidal silica, on theouter surface of each porous particle, in an amount of at least 0.1weight %, based on the total dry weight of the porous particle.

The average size of the discrete pores (or individually isolated andclosed voids or compartments) is described above.

The porous particles can be provided as powders, or as aqueoussuspensions (including water or water with water-miscible organicsolvents such as alcohols). Such powders and aqueous suspensions canalso include surfactants or suspending agents to keep the porousparticles suspended or when rewetting them in an aqueous medium. Auseful surfactant for this purpose, for example is a C₁₂-C₁₄ secondaryalcohol derivative of poly(ethylene oxide) that can be commerciallyavailable as TERGITOL® 15-S-7 (Dow Chemical Corporation). The othercompositional features are described in the incorporated description ofmethods for preparing the porous particles.

The porous particles are generally present in the foamable aqueouscomposition in an amount of at least 0.05 weight % and up to andincluding 15 weight %, or typically at least 0.5 weight % and up to andincluding 10 weight %, based on the total weight of the foamable aqueouscomposition (including water that is present), particularly when theporous particles have a mode size of at least 3 μm and up to andincluding 30 μm.

It is known in the art, that typical white inorganic pigments such astitanium dioxide block electromagnetic radiation by light scattering asa result of refractive index differences between the inorganic pigmentparticles and the surroundings influenced by the pigment particle size.Additionally, there is only so much volume that can be filled (0.635 ofrandom close packing of monodispersed spheres) before interstitialcavities form between packed pigment particles.

The opacity of an opacifying layer is enhanced by interstitial voidsthat are formed when the particle volume concentration (PVC), typicallypigment particles such as titanium dioxide, is above a critical level.The sizes of the interstitial voids for example between the pigmentparticles are smaller than the pigment particles themselves and decreasewith increasing polydispersity of such pigment particles. Since thepigment particle sizes are optimized for maximum light scattering whendispersed in a polymeric matrix above the critical PVC, the interstitialvoids created by the pigment particles will be too small to alsooptimally scatter light. Crowding occurs when the spacing betweenpigment particles decreases to the point where the light scatteringbecomes dependent on the concentration of the pigment particles and theeffectiveness of scattering by the pigment particles is reduced as thepigment loading is increased. This is known as “dependent scattering,” aphenomenon whereby the effective scattering diameter, or scatteringzones, of pigment particles become effectively greater than their actualdiameter. These scattering zones overlap as the concentration ofscattering pigment particles increases, reducing scattering efficiency,and resulting in the crowding effect. Small and large pigment particlesize extenders have been used to create greater separation between thescattering pigment particles and to reduce the overlap of the scatteringzones to result in greater scattering efficiency and opacity.

Advantageously, for the porous particles used in the present invention,the spacing between the light scattering discrete pores within theporous particles is controlled during the process of forming them and isnot subject to subsequent formulation effects such as dependentscattering effects.

Optimal dry opacifying layers designed according to the presentinvention comprise: porous particles containing a small amount of anopacifying colorant as described below to enhance the light-blockingcapacity of the porous particles (particularly transmittedlight-blocking capacity); a binder material to hold the porous particlesin place; and surfactants and other additives including optionally oneor more tinting colorants that can be in other porous particles ordispersed within the layer. The foamed aqueous composition used toprepare the dry opacifying layer comprises foam cells that surround theporous particles.

Upon drying the foamed aqueous composition, the large mismatch inrefractive index between the discrete pores of the porous particles inthe dry opacifying layer and the polymer walls (continuous polymericphase), and the dried foam cells, causes incident electromagneticradiation passing through the dry opacifying layer to be scattered bythe multiplicity of interfaces and discrete pores. The back scatteredelectromagnetic radiation can again be scattered and returned in thedirection of the incident electromagnetic radiation thus reducing theattenuation and contributing to the opacifying power and brightness orluminous reflectance of the dry opacifying layer. If a small amount ofelectromagnetic radiation absorbing opacifying colorant is present inthe porous particles of the dry opacifying layer, for example either inthe discrete pores or in the continuous polymer phase of the porousparticles, the opacifying power of the dry opacifying layer isincreased. This is because the multiple scattering of electromagneticradiation in the dry opacifying layer increases the path length of theelectromagnetic radiation through the dry opacifying layer, therebyincreasing the chance that the electromagnetic radiation will encounterthe opacifying colorant in the dry opacifying layer and be blocked orabsorbed by it.

A single dry opacifying layer present in embodiments of the presentinvention comprises porous particles and a relatively low amount of apredetermined electromagnetic radiation absorbing opacifying colorantsuch as carbon black for creating electromagnetic radiation blockingcoatings and the dry foam cells surrounded by the binder material.Multiple light scattering effects by and among the porous particles andthe surrounding dry foam cells, increase the path of the radiationthrough the dry opacifying layer. The likelihood of radiationencountering an opacifying colorant is increased by this greater pathlength.

Some particularly useful porous particles comprise a continuouspolymeric phase and a first set of discrete pores dispersed within thecontinuous polymeric phase, wherein:

each porous particle has a mode particle size of at least 3 μm and up toand including 30 μm,

each porous particle has a porosity of at least 40 volume % and up toand including 65 volume %,

the continuous polymeric phase comprises one or more polymers, at least70 weight % of which are derived from one or more of cellulose acetate,cellulose butyrate, cellulose acetate butyrate, and cellulose acetatepropionate such that the continuous polymeric phase has a glasstransition temperature (T_(g)) of at least 110° C. and up to andincluding 170° C. as determined using Differential Scanning calorimetry,

the average size of the discrete pores is at least 50 nm and up to andincluding 1000 nm,

the porous particles further comprise a pore stabilizing hydrocolloidwithin at least part of the volume of the discrete pores, which porestabilizing hydrocolloid is selected from the group consisting ofcarboxymethyl cellulose, a gelatin, a protein or protein derivative,polyvinyl alcohol or a derivative thereof, a hydrophilic syntheticpolymer, and a water-soluble microgel, and

the porous particles comprise one or more amphiphilic low HLB blockcopolymers disposed at the interface of one or more of the discretepores and the continuous polymeric phase.

Binder Materials:

The foamable and foamed aqueous compositions used in the presentinvention also comprise one or more binder materials that can behave asa “matrix” for all materials to hold the essential porous particles,additives, opacifying colorants, and any optional materials togetherupon application to the internal surface of the porous substrate anddrying to form a dry opacifying layer.

It is particularly useful that the binder material have the followingproperties: (a) it is water-soluble or water-dispersible; (b) it iscapable of forming a stable foamed aqueous composition with theessential and optional components described herein; (c) it is capable ofbeing disposed onto a suitable substrate as described below; (d) it doesnot inhibit the aeration (foaming) process (described below); (e) it iscapable of being dried and where desired also crosslinked (or cured);(f) it has good light and heat stability; (g) it is film-forming butcontributes to the flexibility of the foamed, opacifying element and isthus not too brittle, for example having a T_(g) of less than 25° C.

The choice of binder material can also be used to increase thelaundering properties of the resulting foamed opacifying compositions inthe foamed, opacifying elements. In addition, the binder material can beused to provide a supple feel to touch and flexibility especially whendisposed on a porous substrate (for example, a fabric) that is meant forwindow coverings such as draperies. The binder material is useful in thefoamed, opacifying element for binding together and adhering the porousparticles and other materials in the dry foamed composition onto theporous substrate.

The binder material can include one or more organic polymers that arefilm forming and that can be provided as an emulsion, dispersion, or anaqueous solution, and that cumulatively provide the properties notedabove. It can also include polymers that are self-crosslinking orself-curable, or it can include one or more polymers to whichcrosslinking agents are added and are thus curable or capable of beingcrosslinked (or cured) under appropriate conditions.

Thus, if the binder material is crosslinkable (or curable) in thepresence of a suitable crosslinking agent, such crosslinking (or curing)can be activated chemically with heat, radiation, or other known means.A curing or crosslinking agent serves to provide improved insolubilityof the resulting dry foamed composition, cohesive strength, and adhesionto the porous substrate. The curing or crosslinking agent is generally achemical having functional groups capable of reacting with reactivesites in a binder material (such as a functionalized latex polymer)under curing conditions to thereby produce a crosslinked structure.Representative crosslinking agents include but are not limited to,multi-functional aziridines, aldehydes, methylol derivatives, andepoxides.

Useful binder materials include but are not limited, to poly(vinylalcohol), poly(vinyl pyrrolidone), ethylene oxide polymers,polyurethanes, urethane-acrylic copolymers, other acrylic polymers,styrene-acrylic copolymers, vinyl polymers, styrene-butadienecopolymers, acrylonitrile copolymers, polyesters, silicone polymers, ora combination of two or more of these organic polymers. Such bindermaterials are readily available from various commercial sources or canbe prepared using known starting materials and synthetic conditions. Thebinder material can be anionic, cationic or nonionic in net charge. Auseful class of film-forming binder materials includes aqueous latexpolymer dispersions such as acrylic latexes that can be ionic ornonionic colloidal dispersions of acrylate polymers and copolymers. Forexample, useful film-forming aqueous latexes include but are not limitedto, styrene-butadiene latexes, poly(vinyl chloride) and poly(vinylidenechloride) latexes, poly(vinyl pyridine) latexes, poly(acrylonitrile)latexes, and latexes formed from N-methylol acrylamide, butyl acrylate,and ethyl acrylate. Examples of suitable commercially available bindermaterials include those sold by DSM under the trade names NEOREZ®A-1150, NEOCRYLs A-6093, by Dow under the trade name RHOPLEX® NW-1845Kand by BASF under the tradenames BUTOFAN® N S144, and BUTOFAN® NS 222,by Lubrizol under the tradenames HYSTRETCH® and HYCAR®, and resins soldby Royal Adhesives such as PARANOL® AC-2032.

The binder material generally has a glass transition temperature that isless than 25° C., and more likely equal to or less than 0° C. Glasstransition temperature can be determined using known procedures and suchvalues are already known for many polymers useful as binder materials inthis invention. The binder material desirably has adequate flexibilityand tensile strength to maintain integrity upon handling, especially foruse with porous textile substrates.

The one or more binder materials can be present in the foamable aqueouscomposition in an amount of at least 20 weight %, or at least 20 weight% and up to and including 60 weight %, or typically at least 30 weight %and up to and including 50 weight %, based on the total foamable aqueouscomposition (that is, the total weight of all components includingwater).

Additives:

The foamable aqueous compositions can include at least 0.0001, or atleast 0.001 weight %, or even at least 0.01 weight %, and up to andincluding 2 weight %, or up to and including 5 weight %, or even up toand including 20 weight %, or even at least and including 30 weight % ofone or more additives comprising at least one surfactant as definedbelow. Other useful additives include but are not limited toplasticizers, inorganic or organic pigments and dyes (for example,pigment or dye colorants different from the opacifying colorantsdescribed below), flame retardants, biocides, fungicides, antimicrobialagents, preservatives, pH buffers, optical brighteners, tintingcolorants, metal particles such as metal platelets or metal flakes,thickeners, and inorganic fillers (such as clays) that are not any ofthe other additive materials or opacifying colorants described below.These amounts refer to the total of the one or more additives in thefoamable aqueous composition and are based on the total weight of thosecompositions (including water). There can be mixtures of each type ofadditive, or mixtures of two or more types of additives in each of thesecompositions.

Any of these additives or mixtures thereof, can be present within anylocation of the foamed aqueous composition, including but not limitedto: the continuous polymeric phase; a volume of the first set (or otherset) of discrete pores; or both the first set (or other set) of discretepores and the continuous polymeric phase of the porous particles.Alternatively, the one or more additives can be present within thebinder material alone, or both within the binder material and within theporous particles.

In all embodiments, the (c) additives useful in the present inventionare not the same compounds as the (a) porous particles, (b) bindermaterials, and (d) opacifying colorants as described herein.

As noted above, at least one additive is a surfactant that is defined asa compound that reduces surface tension in a composition. In mostembodiments of this invention, this essential surfactant is a foamingagent that functions to create and enhance foam formation. In many suchembodiments, the one or more (c) additives comprise one or more foamingagents (surfactants) as well as one or more foam stabilizing agents thatare also surface active agents that function to structure and stabilizethe foam. Examples of useful foaming agents (surfactants) and foamstabilizing dispersing agents include but are not limited to, ammoniumstearate, sodium lauryl sulfate, ammonium lauryl sulfate, ammoniumsulfosuccinate, disodium stearyl sulfosuccinate, ethoxylated alcohols,ionic, nonionic or anionic agents such as fatty acid soaps or a fattyacid condensation product with an alkylene oxide, for example, thecondensation product of ethylene oxide with lauryl or oleic acid or anester of fatty alcohols and similar materials, many of which can beobtained from various commercial sources. Mixtures of foaming agents canbe used if desired.

The relative amounts of each of these two types of (c) additives is notcritical as long as the desired function is evident, that is suitablefoaming properties as required to prepare the foamed aqueous compositionof the present invention, and stability of that foamed aqueouscomposition during storage and manufacture of the foamed, opacifyingelements. The optimal amounts of each of these additives can bedetermined by using routine experimentation and the teaching in theworking Examples below.

Other useful (c) additives include metal particles that can be obtainedfrom any available commercial source as metal flakes or metal plateletsand in dry form or as a suspension. Such metal flakes or metal plateletsare substantially 2-dimensional particles, having opposing main surfacesor faces separated by a relatively minor thickness dimension. The metalflakes can have a size range of at least 2 μm and up to and including 50μm in main surface equivalent circular diameter (ECD) wherein the ECD isthe diameter of a circle having the same area as the main face. Examplesof usable metal flakes include those available from Ciba SpecialtyChemicals (BASF) such as aluminum flakes that are available as METASHEEN91-0410 in ethyl acetate, and copper flakes that can be obtained fromvarious commercial sources. Further details of useful metal flakes areprovided in Cols. 11-12 of U.S. Pat. No. 8,614,039 (Nair et al.), thedisclosure of which is hereby incorporated herein by reference. Themetal particles described above, and particularly the metal flakes canbe in the foamable aqueous composition in any suitable location but theyare particularly useful when incorporated within the porous particlessuch as within the volume of the discrete pores of the porous particles.

Useful biocides (that is, antimicrobial agents or antifungal agents)that can be present as (c) additives include but are not limited to,silver metal (for example, silver particles, platelets, or fibrousstrands) and silver-containing compounds such as silver chelates andsilver salts such as silver sulfate, silver nitrate, silver chloride,silver bromide, silver iodide, silver iodate, silver bromate, silvertungstate, silver phosphate, and silver carboxylates. In addition,copper metal (for example, copper particles, platelets, or fibrousstrands) and copper-containing compounds such as copper chelates andcopper salts can be present as (c) additives for biocidal purposes.Mixtures of any of silver metal, silver-containing compounds, coppermetal, and copper-containing compounds, can also be present and used inthis manner.

It can also be useful to include thickeners as (c) additives to modifythe viscosity of the foamable aqueous composition and to stabilize it aslong as aeration is not inhibited. A skilled worker can optimize theviscosity so as to obtain optimal aeration conditions and desired foamdensity as described below. Useful thickeners can be utilized to controlthe rheology of the foamable aqueous composition depending upon themethod used to form the dry opacifying layer on a porous substrate asdescribed below. Particularly useful rheology modifiers are RHEOVIS® PU1214 (BASF) and ACRYSOL® G111 (Dow Chemical Company).

Particularly useful (c) additives comprise one or more tinting colorantsthat can be used to provide a specific observable color, coloration, orhue in the resulting foamed, opacifying elements. These materials arenot chosen to provide the opacifying property described below for theopacifying colorants and thus, tinting colorants are intended to bedifferent materials than the opacifying colorants.

Mixtures of tinting colorants can be present in the foamable aqueouscompositions and they can be different in composition and amount fromeach other. The desired coloration or hue can be obtained using specifictinting colorants can be used in combination with opacifying colorant(s)described below to offset or modify the original color of a foamed,opacifying element (without such materials) to provide more whiteness(or brightness) in the final “color” (or coloration). The one or moretinting colorants can be incorporated within the porous particles(either within the volume of discrete pores, within the continuouspolymeric phase, or in both places) or they can be uniformly dispersedwithin the binder material. In some embodiments, a tinting colorant canbe incorporated within the same porous particles that also include anopacifying colorant (as described below). Alternatively, one or moretinting colorants can be present within both the porous particles (in asuitable location) and within the binder material.

In some embodiments, a first population of porous particles describedherein comprising opacifying colorants as described below, and anotherpopulation of porous particles described herein comprising tintingcolorants can be mixed with the first population of porous particles.The two sets of porous particles can comprise the same or differentpolymers in the continuous polymeric phase.

The one or more tinting colorants can be present in the foamable aqueouscomposition in an amount of at least 0.0001 weight %, or more typicallyat least 0.001 weight %, and up to and including 3 weight %, based onthe total weight of the foamable aqueous composition (including water).Tinting colorants can be dyes or organic pigments that are soluble ordispersible in organic solvents and polymers that are used for makingthe porous particles and thus can be included within the oil phase usedto prepare such porous particles. Alternatively, the tinting colorantscan be primarily water-soluble or water-dispersible materials andincluded into an aqueous phase used to prepare the porous particles.

It can also be useful to include one or more optical brighteners as (c)additives to increase the whiteness (brightness or “fluorescent” effect)of the final coloration in the foamed, opacifying element. Opticalbrighteners are sometimes known in the art as “fluorescent whiteners” or“fluorescent brighteners.” In general, such materials are organiccompounds selected from classes of known compounds such as derivativesof stilbene and 4,4′-diaminostilbene (such as bistriazinyl derivative);derivatives of benzene and biphenyl (such as styril derivatives);pyrazolines; derivatives of bis(benzoxazole-2-yl); coumarins;carbostyrils; naphthalimides; s-triazines; and pyridotriazoles. Specificexamples of optical brighteners can be found in various publicationsincluding “Fluorescent Whitening Agents,” Kirk-Othmer Encyclopedia ofChemical Technology, Fourth Edition, volume 11, Wiley & Sons, 1994. Oneof more of such compounds can be present in an amount of at least 0.01weight % and up to and including 2 weight %, all based on the totalweight of the foamable aqueous composition.

When present, one or more optical brighteners can be in one or morelocations in the foamable aqueous composition. For example, an opticalbrightener can be present in the binder material. Alternatively, anoptical brightener can be present within: the continuous polymeric phaseof the porous particles; a volume of the discrete pores in the porousparticles; or both in a volume of the discrete pores and the continuouspolymeric phase, of the porous particles.

In many useful embodiments, the (c) additives comprise two or morematerials selected from surfactant that is a foaming agent, a foamstabilizing agent, a tinting agent, an optical brightener, flameretardants, an antimicrobial agent, and an inorganic filler (such as aclay).

(d) Water:

Water is the primary solvent used in the foamable aqueous compositionsused in the present invention. By “primary” is meant that of the totalweight of solvents, water comprises at least 75 weight %, and morelikely at least 80 weight % and up to and including 100 weight % of thetotal solvent weight. Auxiliary solvents that can be present must notadversely affect or harm the other components in the composition, namelythe porous particles, binder materials, one or more additives, andopacifying agents. Nor must such auxiliary solvents adversely affectformation of the foamable aqueous composition or its use to prepare afoamed, opacifying element. Such auxiliary solvents can bewater-miscible organic solvents such as alcohols and ketones.

The solvents then, primarily water, comprise at least 30 weight % and upto and including 65 weight %, or typically at least 40 weight % and upto and including 60 weight %, of the total weight of the foamableaqueous composition.

(e) Opacifying Colorants:

The opacifying colorants used in the present invention can be a singlecolorant or chosen from any suitable combination of colorants such thatthe single or multiple colorants form the “opacifying colorant” thatabsorbs predetermined electromagnetic radiation (defined above) toprovide blackout properties (or suitable opacity). Opacifying colorantscan be soluble dyes or pigments or combinations of each or both types ofmaterials. The opacifying colorants are different from all compoundsdefined above as the (c) additives.

In most embodiments, the one or more opacifying colorants are presentwithin a volume of the first set (or another set) of discrete poreswithin the porous particles, within the continuous polymeric binder ofthe porous particles, or within both the volume of the first set (oranother set) of discrete pores and the continuous polymeric binder ofthe porous particles. This is highly advantageous as the porousparticles can be used to “encapsulate” various opacifying colorants aswell as tinting colorants and other (c) additives so they are keptisolated from the other components of the foamable aqueous compositionand are additionally not exposed to the environment during sewing orupon surface damage of the foamed, opacifying element. However, in someembodiments, it can be useful to incorporate opacifying agents solely oradditionally within the binder material in which the porous particlesare dispersed.

As used herein, an “opacifying colorant” includes one or more colorantmaterials that are chosen, individually or in combination, to providethe blocking of predetermined electromagnetic radiation (as describedabove). While the opacifying colorants can provide some coloration ordesired hue, they are not purposely chosen for the purpose and are thusmaterials that are chosen to be different from the tinting colorantsdescribed above.

Examples of opacifying colorants that can be used individually or incombination include but are not limited to, neutral or black pigments ordyes, a carbon black, black iron oxide, graphite, aniline black,anthraquinone black, and combinations of colored pigments or dyes suchas combinations of two or more cyan, magenta, green, orange, blue, red,and violet dyes. The present invention is not limited to only thespecific opacifying colorants described herein but these are consideredas representative and as suitable guidance for a skilled worker todevise other combinations of opacifying colorants for the desiredabsorption in the predetermined electromagnetic radiation. A carbonblack or a neutral or black pigment or dye (or combination thereof) isparticularly useful as an opacifying colorant, of which there are manytypes available from commercial sources. Combinations of dyes orpigments such as a combination of the subtractive primary coloredpigments (cyan, magenta, and yellow colored pigments) can also be usedto provide a “black” or visually neutral opacifying colorant.

The opacifying colorant can be generally present in the foamable aqueouscomposition in an amount of at least 0.001 weight % and up to andincluding 0.5 weight %, or at least 0.003 weight % and up to andincluding 0.2 weight %, all based on the total weight of the foamableaqueous composition (including the weight of solvent). These amountsrefer to the total amount of one or a mixture of opacifying colorants.For example, as noted above, an opacifying colorant can comprise acombination of two or more component colorants (such as a combination ofdyes or a combination of pigments) designed in hues and amounts so thatthe combination meets the desired properties described herein.

In some embodiments, the opacifying colorant is a carbon black that ispresent in an amount of at least 0.003 weight % and up to and including0.2 weight %, based on the total weight of the foamable aqueouscomposition.

In some embodiments, the opacifying colorants, if in pigment form, canbe milled to a fine particle size and then encapsulated within thevolume of the discrete pores of the porous particles by incorporatingthe milled pigment within an aqueous phase used in making the porousparticles. Alternatively, the opacifying colorant can be incorporatedwithin the continuous polymeric phase of the porous particles byincorporating the opacifying colorant in the oil phase used in makingthe porous particles. Such arrangements can be achieved during themanufacture of the porous particles using the teaching provided hereinand teaching provided in references cited herein.

In some embodiments, it can be useful to incorporate or dispose at least95% (by weight) of the total opacifying colorant (or combination ofcomponent colorants) within the porous particles (either in the volumeof the discrete pores, continuous polymeric phase, or both), and toincorporate the remainder, if any, within the binder material. However,in many embodiments, 100 weight % of the opacifying colorant isincorporated within the porous particles. For example, more than 50weight % of the total opacifying colorant can be disposed orincorporated within the continuous polymeric phase of the porousparticles, and the remainder can be incorporated within the volume ofthe discrete pores.

The opacifying colorants useful in the practice of this invention can beincorporated into the volume of the discrete pores of individual porousparticles for example, by incorporating them in a first water phase toform a water-in-oil emulsion or in the continuous polymeric phase of theindividual porous particles by incorporating them in the oil phase. Insome embodiments, an opacifying colorant can be incorporated into thefirst aqueous phase in the form of a milled solid particle dispersionsof the opacifying colorant. Preparation of milled solid particledispersions can include combining the opacifying colorant particles tobe reduced in size with a dispersant and a liquid medium such as wateror ethyl acetate (when the opacifying colorant is incorporated in thecontinuous polymeric phase of the particle) in which the porousparticles are to be dispersed, in a suitable grinding mill in which theporous particles are reduced in size and dispersed. The dispersant, animportant ingredient in the milling, can be chosen to allow theopacifying colorant particles to be milled in the liquid medium down toa size small enough for incorporation into the discrete pores of theporous particles. The dispersants can be selected to obtain efficientopacifying colorant particle size reduction during milling, provide goodcolloidal stability of the opacifying colorant particles to preventagglomeration after milling and impart the desired properties of thefinal foamed aqueous composition containing the opacifying colorants andthe porous particles containing them. Alternatively, the opacifyingcolorant also can be incorporated in the continuous polymeric phase as amaster batch of the opacifying colorant and an appropriate resin.

Foamed Aqueous Compositions

Foamed aqueous compositions can be prepared using the proceduresdescribed below wherein an inert gas (such as air) is mechanicallyincorporated into the foamable aqueous composition as described above,which procedures are designed to provide a foam density of at least 0.1g/cm² and up to and including 0.5 g/cm³, or more likely of at least 0.15g/cm³ and up to and including 0.4 g/cm³. Foam density can be determinedgravimetrically by weighing a known volume of the foamed aqueouscomposition.

The foamed aqueous composition generally has at least 35% solids and upto and including 70% solids, or more particularly at least 40% solidsand up to and including 60% solids.

The essential components (a) through (e) of the foamed aqueouscomposition are generally present in the same amounts as in the foamableaqueous composition (described above) as the foaming process does notappreciably add to or diminish the amounts of such components.

For example, the (a) porous particles (as described above) can bepresent in the foamed aqueous composition in an amount of at least 0.05weight % and up to and including 15 weight %, or typically of at least0.5 weight % and up to and including 10 weight %, based on the totalweight of the foamed aqueous composition.

One or more (b) binder materials (as described above) can be present inan amount of at least 20 weight %, or at least 25 weight % and up to andincluding 70 weight % or typically of at least 30 weight % and up to andincluding 50 weight %, based on the total weight of the foamed aqueouscomposition. In addition, one or more of the binder materials in thefoamed aqueous composition can be curable.

One or more (c) additives (as described above) can be present in anamount of at least 0.0001 weight % and up to and including 30 weight %or typically of at least 0.001 weight %, or even at least 0.01 weight %,and up to and including 20 weight %, based on the total weight of thefoamed aqueous composition. At least one of the (c) additives is asurfactant as described above, and in particularly useful embodiments,the (c) additives comprise a foaming agent and a foam stabilizing agent.Other useful (c) additives can be present as noted above for thefoamable aqueous compositions, also in the amounts noted above. Forexample, some particularly useful embodiments of the foamed aqueouscomposition, the (c) additives comprise two or more materials selectedfrom surfactant that is a foaming agent, a surfactant that is a foamdispersing agent, a tinting agent, an optical brightener, a flameretardant, an antimicrobial agent, and an inorganic filler (such as aclay).

Component (d), water, is also present as the predominant solvent (atleast 75 weight % of total solvent weight), and all solvents that arepresent in an amount of at least 30 weight % and up to and including 70weight %, or typically at least 40 weight % and up to and including 60weight %, based on the total weight of the foamed aqueous composition.

The (e) opacifying colorants (as described above) are generally presentin any suitable amount to provide the desired appearance, coloration,and opacity in the resulting foamed (and dried) opacifying element. Inmany embodiments, the one or more opacifying colorants can be present inan amount of at least 0.001 weight % or at least 0.001 weight % and upto and including 0.5 weight %, or even in an amount of least 0.003weight % and up to and including 0.2 weight %, especially when theopacifying colorant is a carbon black, all weights based on the totalweight of the foamed aqueous composition.

In some embodiments, the foamed aqueous composition comprises at least0.5 weight % and up to and including 10 weight % of the porous particles(as described above) that have a mode particle size of at least 3 μm andup to and including 30 μm, the amount based on the total weight of thefoamed aqueous composition. In addition, discrete pores in such porousparticles can have an average pore size of at least 100 nm and up to andincluding 7000 nm.

Moreover, the foamed aqueous composition can further comprise at least0.001 weight % of the opacifying colorant (described above) within theporous particles. For example, some opacifying colorant can be a carbonblack and present in an amount of at least 0.003 weight % and up to andincluding 0.2 weight % based on the total weight of the foamed aqueouscomposition.

Such opacifying colorant can be within: (i) the continuous polymericphase of the porous particles; (ii) a volume of the discrete pores; or(iii) both the volume of the discrete pores and the continuous polymericphase of the porous particles.

In some embodiments of the foamed aqueous composition, porous particlescan be used that further comprise at least a second set of discretepores (different from a “first” set of discrete pores) and an opacifyingcolorant or a tinting colorant can be present within: the continuouspolymeric phase, the volume of the second set of discrete pores, or inboth the continuous polymeric phase and the volume of the second set ofdiscrete pores. First and second sets (or additional sets) of discretepores can be incorporated into the porous particles using manufacturingtechnology described in several references cited above, including U.S.Pat. No. 8,110,628 (Nair et al.).

Foamed, Opacifying Elements

Foamed, opacifying elements according to the present invention can beprepared using methods described below. Such articles comprise a poroussubstrate and at least one dry foamed composition disposed on theinternal surface of the porous substrate to form a dry opacifying layer.As described in more detail, each porous substrate has two supporting(planar) sides, that is, an opposing external surface and internalsurface as defined above).

Each dry foamed composition is derived from a foamed aqueous compositionas described above. Each dry foamed composition comprises at least theessential components (a) through (e) described above, all of which andrespective amounts are described in more detail above.

Component (a) porous particles are present in an amount of at least 0.1weight % and up to and including 40 weight % or at least 0.5 weight %and up to and including 10 weight % of porous particles that aredescribed in detail above, the amounts based on the total weight of thedry foamed composition, particularly when the porous particles have amode particle size of at least 2 μm and up to and including 50 μm (or atleast 3 μm and up to and including 30 μm) and the first set of discretepores of the porous particles have an average pore size of at least 100nm and up to and including 7,000 nm.

In addition, the dry foamed composition includes component (b) bindermaterial in an at least partially cured or crosslinkable form, which isat least 10 weight % and up to and including 70 weight %, or at least 20weight % and up to and including 60 weight % of one or more at leastpartially cured binder materials. Such at least partially cured bindermaterials are derived by at least partial curing or crosslinking(described below) of the binder materials described above. The notedamounts are based on the total weight of the dry foamed composition.Each of the one or more binder materials has a T_(g) of 25° C. or less,or 0° C. or less.

One or more (c) additives, at least one is a surfactant, are present inan amount of at least 0.2 weight % and up to and including 50 weight %,or at least 1 weight % and up to and including 45 weight %, suchadditives being selected from the group consisting of foaming agents,foam stabilizing agents, plasticizers, inorganic or organic pigments anddyes (for example, pigment or dye colorants different from theopacifying colorants described below), flame retardants, antimicrobials,fungicides, preservatives, pH buffers, optical brighteners, tintingcolorants, metal particles such as metal platelets or metal flakes,thickeners, and inorganic fillers (such as clays) that are not any ofthe other additive materials or opacifying colorants described herein,all of which additives are described in more detail above. The amountsare based on the total weight of the dry foamed composition. As notedabove, most embodiments include at least one surfactant that is afoaming agent and at least one foam stabilizing agent.

Particularly useful one or more (c) additives comprise two or morematerials selected from a foaming agent, a foam stabilizing agent, atinting colorant, an optical brightener, a flame retardant, anantimicrobial agent, and an inorganic filler (such as a clay).

Thus, the foamed, opacifying element can comprise one or more tintingcolorants as (c) additives in the dry foamed composition in an amount ofat least 0.0001 weight % and up to and including 3 weight %, based onthe total weight of the dry foamed composition. Such tinting colorant(s)can be present in at least the porous particles, and can be elsewherealso.

It is also useful to include one or more optical brighteners as (c)additives in an amount of at least 0.001 weight % and. up to andincluding 0.4 weight %, based on the total weight of the dry foamedcomposition.

The dry foamed composition is “substantially” dry in nature, meaningthat it comprises less than 5 weight %, or even less than 2 weight %, ofaqueous medium (including water and any other solvents), based on thetotal weight of the dry foamed composition. This amount may not includeany water that can be present in the discrete pores of the porousparticles. The dry foamed composition in the dry opacifying layergenerally comprises at least 90% solids, or at least 95% solids, or evenat least 98% solids.

The dry foamed composition can also contain at least 0.002 weight %, oreven at least 0.02 weight % and up to and including 2 weight % or up toand including 1 weight %, of one or more (e) opacifying colorants (asdescribed above), which opacifying colorants absorb all wavelengths ofthe predetermined electromagnetic radiation (as defined above). Detailsof such opacifying colorants are described above, and the amounts arebased on the total weight of the dry foamed composition. Such opacifyingcolorants can be present within the (a) porous particles or within the(b) binder material, or within both (a) and (b) components.

In some embodiments, a carbon black is present as the (e) opacifyingcolorant in an amount of at least 0.002 weight % and up to and including1 weight %, based on the total weight of the dry foamed composition.

In many embodiments of the foamed, opacifying element, the opacifyingcolorant (such as a carbon black) can be present within: the continuouspolymeric phase of the porous particles; a volume of the discrete pores;or both the volume of the discrete pores and the continuous polymericphase of the porous particles.

The foamed, opacifying elements are designed particularly to have asingle dry opacifying layer with the components disposed on the poroussubstrate so that the single dry opacifying layer in an element exhibitsa light-blocking value (LBV) of at least 4 or more likely at least 5.For this purpose, light-blocking value can be determined as describedabove.

In addition, such dry opacifying layers exhibit a luminous reflectance(opacity) that is greater than 40%, as measured for the Y tristimulusvalue. For this purpose, luminous reflectance (brightness) is determinedas described above.

Dry porous substrates useful in the practice of the present inventioncan comprise various porous materials such as knit, woven and nonwoventextile fabrics composed of polyester, polyamides, triacetate, acrylic,elastomers, nylon, or mixtures thereof, or knit, woven and nonwovenfabrics of cotton, linen, rayon, polyolefin, cotton, wool, porousglasses, fiberglass fabrics, or felt or mixtures thereof, or porouspolymeric films [such as porous films derived from triacetyl cellulose,polyethylene terephthalate (PET), diacetyl cellulose, acetate butyratecellulose, acetate propionate cellulose, polyether sulfone, polyacrylicbased resin, for example, poly(methyl methacrylate), apolyurethane-based resin, polyester, polycarbonate, aromatic polyamide,polyolefins (for example, polyethylene and polypropylene), polymersderived from vinyl chloride (for example, polyvinyl chloride and a vinylchloride/vinyl acetate copolymer), polyvinyl alcohol, polysulfone,polyether, polynorbornene, polymethylpentene, polyether ketone,(meth)acrylonitrile], porous paper or other porous cellulosic materials,canvasses, porous wood, porous plaster and other porous materials thatwould be apparent to one skilled in the art. The porous substrates canvary in dry thickness as long as they are suitable for the desiredfoamed, opacifying element. In most embodiments, the dry poroussubstrate thickness is at least 50 μm.

Particularly useful porous substrates comprise a porous textile web(such as a flexible porous textile web) composed of synthetic materialssuch as polyester, nylon, acrylic materials, or synthetic blends withnatural fibers.

Generally, the foamed, opacifying elements according to this inventionare designed with a single dry opacifying layer disposed on the internalsurface of the porous substrate as described above and such single dryopacifying layer can be the outermost layer disposed on the internalporous substrate. In some other embodiments, a dry non-opacifying layercan be disposed on the single dry opacifying layer, or it can bedisposed on the opposing external surface of the porous substrate. Sucha dry non-opacifying layer can be designed with any of the components(a) through (c) described above, but it does not comprise an (e)opacifying colorant as defined herein. Useful dry non-opacifying layerscan be designed to have various functions such as coefficient offriction, texture and feel, antimicrobial properties, anti-blocking, andcolor modification.

Attractive finishes can be imparted to the foamed, opacifying element byfor example, flocking the foamed aqueous composition that is disposed onthe porous substrate. Flock or very short (0.2 mm and up to several mm)fibers can be disposed on the foamed aqueous composition either byelectrostatic or mechanical techniques before or during drying.

Either the dry opacifying layer or dry non-opacifying layer can betreated with an anti-blocking agent such as a silicone, to reducestickiness and to improve the surface coefficient of friction. Onceapplied, a blocking agent can be dried on the appropriate layer.

A thermal colorant image that is derived from a thermal coloranttransfer process is disposed on at least the opposing external surfaceof the porous substrate, the dry opacifying layer, or on both theopposing external surface and the dry opacifying layer in the foamed,opacifying element. Details about providing such thermal colorantimaging are provided below.

Methods of Making Foamed, Opacifying Elements

The foamed, opacifying elements are prepared by firstly providing a dryopacifying layer from a foamable aqueous composition as described abovecomprising essential components (a) through (e) in the describedamounts.

This foamable aqueous composition is aerated to provide a foamed aqueouscomposition having a foam density of at least 0.1 g/cm³ and up to andincluding 0.5 g/cm³, or of at least 0.15 g/cm³ and up to and including0.4 g/cm³. This aeration procedure can be carried out using any suitableconditions and equipment that would be readily apparent to one skilledin the art in order to create a “foam” in the presence of a foamingagent as the (c) additive surfactant described above. For example,aeration can be carried out by mechanically introducing air or an inertgas (such as nitrogen or argon) in a controlled manner. High shearmechanical aeration can be carried out using sonication or high speedmixers, such as those equipped with a cowles blade, or with commerciallyavailable rotorstator mixers with interdigitated pins such as an Oakesmixer or a Hobart mixer, by introducing air under pressure or by drawingatmospheric air into the foamable aqueous composition by the whippingaction of the mixer. Suitable foaming equipment can be used in a mannerto provide the desired foam density with modest experimentation. It canbe useful to chill or cool the foamable aqueous composition belowambient temperature to increase its stability by increasing itsviscosity, and to prevent collapse of the foamed aqueous composition.This chilling operation can be carried out immediately before, after, orduring the aeration procedure. Stability of the foamed aqueouscomposition can also be enhanced by the presence of a foam stabilizingagent as another of the (c) additives.

Once the foamed aqueous composition has been formed, it is typicallydisposed onto the internal surface of a suitable porous substrate(described above). This procedure can be carried out in any suitablemanner that does not undesirably diminish the foam density (or foamstructure) of the foamed aqueous composition. For example, the internalsurface of the porous substrate can be coated with the aqueous foamedcomposition using any suitable known coating equipment (floating knife,hopper, blade, or gap) and coating procedures including but not limitedto blade coating, gap coating, slot die coating, X-slide hopper coating,or “knife-over-flat” operation, especially if multiple layers areapplied to the internal surface. If the dry opacifying layer is the onlylayer to be formed on the internal surface, the foamed aqueouscomposition can be applied using blade coating, gap coating, slot diecoating, or “knife-over-flat” coating. For example, useful layer forming(coating) means are described in U.S. Pat. No. 4,677,016 (noted above),the disclosure of which is hereby incorporated herein by reference.

Thus, the foamed aqueous composition can be disposed directly onto theinternal surface of the porous substrate (“directly” means nointervening or intermediate layers) such as a porous woven cloth fabric,a fiberglass fabric, a porous polyester fabric, or a cellulosicmaterial.

When multiple layers are to be disposed on the internal surface of theporous substrate, a single dry opacifying layer can be disposed thereonand an outermost non-opacifying layer can be disposed on the dryopacifying layer using a suitable coating means as described above.Alternately, a non-opacifying layer can be disposed on the internalsurface underneath the dry opacifying layer.

Once the foamed aqueous composition has been disposed on the internalsurface of the porous substrate, it is dried to remove at least 95% ofthe original water, and at least partially cured (meaning the one ormore binder materials are at least partially cured or crosslinked),simultaneously or in any order, to provide a dry foamed composition (anddry opacifying layer) on the internal surface of the porous substrate.Drying and at least partial curing can be accomplished by any suitablemeans such as by heating with warm or hot air, microwaves, or IRirradiation at a temperature and time sufficient for at least drying andat least partial curing (for example, at less than 180° C.). Curing thebinder materials can be promoted by heat or radiation or otherconditions to which the binder materials are responsive forcrosslinking. In some embodiments, a suitable functionalized latexcomposition is used as the binder material. Upon heating, the bindermaterial(s) dries, and a possible curing or crosslinking reaction takesplace between reactive side groups of suitable curable polymer chains.If the particular binder material is not itself heat reactive, suitablecatalysts or curing (crosslinking) agents can be added to the foamableaqueous composition to promote curing or crosslinking.

After drying and at least partially curing, the dry foamed compositionon the internal surface is then crushed or densified to form a dryopacifying layer. This process can be carried out in any suitable mannerbut it is generally carried out by applying pressure to the dry foamedcomposition on the internal surface, for example, by passing the poroussubstrate with the dry foamed composition through a compressioncalendering operation, pressing operation, or embossing operation, or acombination thereof. For example, the foamed, opacifying element can bepassed through a combination of calendering and embossing rollers toreduce the thickness of the dry foamed composition and to densify thefoam. The thickness of the dry foamed composition can be reduced by atleast 20% during such an operation. This process of crushing the dryfoamed composition can be considered a “densifying operation” as the dryfoamed composition is made denser while it is pressed together on theinternal surface. The thickness of the dry foamed composition before andafter crushing (densifying) can be determined by a known technique suchas laser profilometry. After drying and crushing, the foamed, opacifyingelement generally has a light-blocking value (LBV) of at least 4, or atleast 5, which LBV is determined as described above.

The crushing or densifying process described above can be carried out atany suitable temperature including room temperature (for example, 20°C.) and up to and including 90° C., or more likely at a temperature ofat least 20° C. and up to and including 80° C.

After densifying the dry foamed composition, the dry opacifying layercan be subjected to conditions that promote further curing such as thoseconditions that are described above for the initial drying operations.

It is also possible to provide an embossed design on the outermostlayer, for example, on the dry opacifying layer or on a drynon-opacifying layer during the densifying operation such as forexample, by patterned embossing or calendering the dry outermost layer,to create selected regions of high or low opacity and thickness. Theresulting embossed design can be viewed from either side intransmission.

Providing Thermal Dye Images

As described above, the foamed, opacifying elements according to thepresent invention comprise one or more thermal colorant images disposedon either the opposing external surface, the dry opacifying layer (onthe internal surface), or both the opposing external surface and the dryopacifying layer. Each of these thermal colorant images is obtainedusing thermal colorant transfer processes that are described in moredetail below. In most embodiments, the one or more thermal colorantimages (such as thermal dye images) are provided on only the opposingexternal surface of the porous substrate.

In some embodiments, a thermal colorant image can be provided by aprocess that can be called “direct disperse dye printing” in which oneor more thermal colorants are applied to a pretreated fabric substratewithout the use of a thermal donor element and heated thereon to“thermofix” them into the pretreated fabric substrates.

In general, such thermal colorant images are provided by superposing acolorant donor layer of a thermal donor element (described below) andthe surface of the foamed, opacifying element to be printed (or imaged).For example, the opposing external surface of the porous substrate andthe colorant donor layer can be superposed, or the dry opacifying layerand the colorant donor layer can be superposed. In any of thesearrangements, the desired thermal colorant image (pattern) istransferred by suitable application of heat, with or without pressure,that is directed to the superposed articles from the “backside” of thethermal donor element (thermal donor element support side opposite thecolorant donor layer).

By the term “superposing” is meant that the colorant donor layer and thefoamed, opacifying element are in intimate contact with little or no airgap.

Thermal donor elements useful in the practice of this invention can beprovided in a variety of ways. For example, a thermal donor element canbe obtained from a variety of commercial sources and such thermal donorelements typically comprise a suitable paper (cellulosic) or polymeric(such as polyester) support onto which a single- or multi-color image(or pattern) of one or more “inks” have been applied using inkjetprinting, gravure printing, rotary screen printing, or other means. Suchsingle- or multi-color image (or pattern) is provided as a “mirror”(negative) image or pattern so that the image or pattern provided on thefoamed, opacifying element is a “positive” image or pattern.

In other embodiments, a thermal donor element can be provided like thosecommercially available from various sources worldwide. Such elements aresometimes referred to as thermal dye ribbons and have various colorsthat can be thermally printed, or they can have various colored dyepatches on a single web or roll of thermal donor material. Eachindividual ribbon or patch comprises the appropriate sublimable dyes.

In such embodiments, the thermal colorant donor elements generallycomprises a support having thereon a colorant donor layer (for example,a dye donor layer) comprising at least one thermally transferablecolorant such as a sublimable dye or pigment. Such transferablecomposition can also be known as an “ink”.

Many useful inks or dye colorants are known in the commercial trade orliterature and the present invention is not limited to specificmaterials as long as they can be incorporated into a colorant dye donorlayer and transferred to the foamed, opacifying element described above.Representative thermal donor elements can be constructed as described inU.S. Pat. No. 4,916,112 (Henzel et al.), U.S. Pat. No. 4,927,803 (Baileyet al.), U.S. Pat. No. 5,023,228 (Henzel), and U.S. Pat. No. 7,153,626(Foster et al.), the disclosures of all of which are incorporated hereinby reference.

In some of these embodiments, a thermal donor element can comprise apaper (cellulosic) or polymeric (such as polyester) support coating orinkjet printed image in a ribbon having sequential repeating areas(patches), or patterns or cyan, magenta, yellow, or black dye or ink.Thermal colorant transfer can be carried out sequentially orsimultaneously to provide multi-color images.

As used herein, a thermally transferable “ink” can comprise one or moredyes, pigments, or other colorants and optionally one or more bindermaterials or carriers as would be readily apparent to one skilled in theart. Thermally transferable colorants such as dyes can be selected bytaking into consideration of hue, lightfastness, solubility in anybinder material, type of support, and thermal transfer conditions. Manyexamples of useful thermally transferable dyes are described in thereferences cited in [0115] of U.S. Patent Application Publication2014/0071218 (Dontula et al.), the disclosure of which is incorporatedherein by reference, including all US publications cited therein.

Useful thermally transferable colorants such as dyes can be employedsingly or in combination and can be provided in a thermal donor elementin an amount of at least 0.01 g/m² and up to and including 5 g/m², ormore likely at least 0.05 g/m² and up to and including 2 g/m² based onthe dry coverage of a colorant donor layer.

Representative sublimable dyes (inks) that can be used in the practiceof this invention include Kiian Digistar E-Gold Sublimation Inks forTransfer Printing that can be applied to a substrate such as KiianDigistar Paper using Epson piezo printheads in any desired pattern orimage. The resulting thermal donor element can be used immediately orstored for later use. Thermal transfer of the ink from the thermal donorelement to the foamed, opacifying element can be carried out using anysuitable thermal transfer equipment such as a Practix OK-405 RotaryTransfer Machine that has a heated cylinder or calendaring roll againstwhich the thermal donor element and desired surface of a poroussubstrate to be printed are superposed by means of an endless belt andin contact between the heated cylinder and the endless belt. In general,thermal transfer can be done with a heat press for sheets, or with aheated calendaring roller for rolls of material.

In many embodiments, image transfer can be accomplished by applying heatof at least 180° C. and up to and including 220° C., for example at 200°C., optionally at a suitable pressure. The dwell time desired foradequate sublimation, transfer, and condensation of the images isgenerally at least 15 seconds and up to and including 90 seconds, suchas at least 30 seconds and up to and including 60 seconds. Temperatureand time for this thermal transfer process can be adjusted by a skilledartisan using routine experimentation so that at least 60 weight %, oreven at least 80 weight % of the colorant (ink) in the thermal donorelement is transferred to the foamed, opacifying element. The amount ofsuch thermal transfer can be evaluated by measuring the weight ofthermal donor element before and after thermal image transfer, or bymeasuring the transmission density of the image or pattern on thethermal donor element before and after thermal image transfer using acommercial densitometer.

In addition to providing a colored image or pattern by thermal transfer,the present invention can also include providing a protective clear film(laminate) to the porous substrate by thermal transfer. Such protectiveclear film or overcoat can be applied over the thermally transferredcolorant image or pattern, or on a surface opposite the thermallytransferred colorant image or pattern. This protective clear film can beprovided with a separate thermal donor element (or ribbon) for exampleas described in U.S. Patent Application Publication 2010/0218887(Vreeland et al.), the disclosure of which is incorporated herein byreference. Other details of such clear laminates are provided in[0118]-[0120] of U.S. '887 (noted above). Alternatively, the protectiveclear film can be provided as a separate patch in a thermal donorelement that has one or more thermally transferable colorant patches aswell as a patch to supply the protective clear film.

For example, in some embodiments, a protective clear film can bethermally applied (printed) over a color thermally printed image orpattern on the opposing external side of the porous substrate. In otherembodiments, a protective clear film can be thermally applied (printed)over a color thermally printed image or pattern on the dry opacifyinglayer on the internal side of the porous substrate. In yet otherembodiments, a protective clear film can be thermally applied (printed)on the opposing external surface that does not have a color thermallyprinted image or pattern, but such color thermally printed image orpatterns is disposed on the dry opacifying layer on the internal side ofthe porous substrate.

The present invention can also be used to thermally transfer metalimages or patterns for various metallic effects on a thermallytransferred color image on either side of the porous substrate using auniquely designed thermal donor element containing transferable metalsinstead of dyes or other colorants in a metal donor layer. Details aboutsuch materials and uses thereof are described in [0121] of US '218(noted above) and publications cited therein.

The present invention provides at least the following embodiments andcombinations thereof, but other combinations of features are within thepresent invention as a skilled artisan would appreciate from theteaching of this disclosure:

1. A foamed, opacifying element comprising a thermal colorant image, thefoamed, opacifying element further comprising a porous substrate havingan opposing external surface and an internal surface, the internalsurface having a dry foamed composition disposed thereon as a dryopacifying layer,

wherein the dry foamed composition comprises:

(a) at least 0.1 weight % and up to and including 40 weight % of porousparticles, each porous particle comprising a continuous polymeric phaseand a first set of discrete pores dispersed within the continuouspolymeric phase, the porous particles having a mode particle size of atleast 2 μm and up to and including 50 μm and a porosity of at least 20volume % and up to and including 70 volume %, and the continuouspolymeric phase having a glass transition temperature greater than 80°C. and comprising a polymer having a viscosity of at least 80centipoises and up to and including 500 centipoises at a shear rate of100 sec⁻¹ in ethyl acetate at a concentration of 20 weight % at 25° C.;

(b) at least 10 weight % of an at least partially cured binder material;

(c) at least 0.2 weight % of one or more additives comprising asurfactant;

(d) less than 5 weight % of water; and

(e) at least 0.002 weight % of an opacifying colorant different from allof the one or more (c) additives, which opacifying colorant absorbspredetermined electromagnetic radiation,

all amounts being based on the total weight of the dry foamedcomposition,

wherein the dry opacifying layer has a light blocking value of at least4 as well as a luminous reflectance that is greater than 40% as measuredby the Y tristimulus value, and

wherein the thermal colorant image that is derived from thermal coloranttransfer is disposed on the opposing external surface, the dryopacifying layer, or both the opposing external surface and the dryopacifying layer.

2. The foamed, opacifying element of embodiment 1, wherein the poroussubstrate comprises a porous textile web, porous polymer film, porouscellulosic material, porous ceramic material, or porous glass material.

3. The foamed, opacifying element of embodiment 1 or 2, wherein theporous substrate comprises a polyester.

4. The foamed, opacifying element of any of embodiments 1 to 3, whereinthe dry opacifying layer is the only layer disposed on the poroussubstrate.

5. The foamed, opacifying element of any of embodiments 1 to 3, furthercomprising a dry non-opacifying layer disposed on the dry opacifyinglayer.

6. The foamed, opacifying element of embodiment 5, wherein the drynon-opacifying layer comprises a tinting colorant, a flame retardant, anantimicrobial agent, an anti-blocking agent, or a flocking agent.

7. The foamed, opacifying element of any of embodiments 1 to 6, whereinthe dry opacifying layer exhibits a light blocking value of at least 5.

8. The foamed, opacifying element of any of embodiments 1 to 7, whereinthe continuous polymeric phase comprises at least 70 weight %, based onthe total polymer weight in the continuous polymeric phase, of one ormore polymers derived from one or more of cellulose acetate, cellulosebutyrate, cellulose acetate butyrate, and cellulose acetate propionate.

9. The foamed, opacifying element of any of embodiments 1 to 8, whereinthe opacifying colorant is a carbon black that is present in an amountof at least 0.002 weight % and up to and including 1 weight %, based onthe total weight of the dry foamed composition.

10. The foamed, opacifying element of any of embodiments 1 to 9, whereinthe dry foamed composition comprises at least 0.5 weight % and up to andincluding 10 weight % of the porous particles, based on the total weightof the dry foamed composition, which porous particles have a modeparticle size of at least 3 μm and up to and including 30 μm.

11. The foamed, opacifying element of any of embodiments 1 to 10,wherein:

the dry foamed composition has at least 98% solids;

the continuous polymeric phase comprises at least 70 weight % and up toand including 100 weight %, based on the total polymer weight in thecontinuous polymeric phase, of one or more polymers derived from one ormore of cellulose acetate, cellulose butyrate, cellulose acetatebutyrate, and cellulose acetate propionate;

the porous particles are present in an amount of at least 0.5 weight %and up to and including 10 weight %;

the at least partially cured binder material is present in an amount ofat least 20 weight % and up to and including 60 weight % and has a glasstransition temperature of less than 25° C.;

the one or more (c) additives further comprise an optical brightener inan amount of at least 3 weight % and up to and including 45 weight %;

carbon black is present as at least one opacifying colorant in an amountof at least 0.002 weight % and up to and including 1 weight %; and

the dry opacifying layer has a light blocking value of at least 5,

all amounts based on the total weight of the dry foamed composition.

12. The foamed, opacifying element of any of embodiments 1 to 11,wherein the one or more (c) additives further comprise metal flakes thatare present within the porous particles.

13. The foamed, opacifying element of any of embodiments 1 to 12,wherein the surfactant of the one or more (c) additives is a foamingagent and the one or more (c) additives further comprise a foamstabilizing agent.

14. The foamed, opacifying element of any of embodiments 1 to 13,wherein the one or more (c) additives further comprise a tintingcolorant in an amount of least 0.0001 weight % and up to and including 3weight %, based on the total weight of the dry foamed composition.

15. The foamed, opacifying element of any of embodiments 1 to 14,wherein the one or more (c) additives further comprise an opticalbrightener in an amount of at least 0.001 weight % and up to andincluding 0.4 weight %, based on the total weight of the dry foamedcomposition.

16. The foamed, opacifying element of any of embodiments 1 to 15,wherein the one or more (c) additives comprise an antimicrobial agentcomprising silver metal, a silver-containing compound, copper metal, acopper-containing compound, or a mixture of any of these.

17. The foamed, opacifying element of any of embodiments 1 to 16,wherein the thermal colorant image comprises a sublimed cyan, yellow,magenta, or black dye, or a combination thereof.

18. The foamed, opacifying element of any of embodiments 1 to 17,wherein the thermal colorant image further comprises metal particlesprovided by thermal transfer.

19. The foamed, opacifying element of any of embodiments 1 to 18,wherein the thermal colorant image is a multi-color image on theopposing external surface of the porous substrate.

20. The foamed, opacifying element of any of embodiments 1 to 19,further comprising a transparent protective layer over the thermalcolorant image.

The following Examples are provided to illustrate the practice of thisinvention and are not meant to be limiting in any manner. The followingmaterials were used in the Examples.

Materials used in the Following Examples:

The continuous polymeric phase polymers used in the following exampleswere the Eastman™ Cellulose Acetate Butyrate 381-0.5 (CAB), a celluloseester, T_(g) of 130° C. (obtained from Chem Point);

NALCO® 1060 containing colloidal silica was obtained from Nalco ChemicalCompany as a 50 weight % aqueous dispersion.

The poly(methylamino ethanol adipate) (AMAE) co-stabilizer was preparedusing known procedures and starting materials.

Carboxy methylcellulose (CMC, 250,000 kDa) was obtained from AcrosOrganics or from Ashland Aqualon as Aqualon 9M31F. These products wereused interchangeably.

The amphiphilic block copolymer of polyethylene oxide andpolycaprolactone (PEO-b-PCL) 5K-20K, was prepared using the proceduredescribed in U.S. Pat. No. 5,429,826 (Nair et al.), the disclosure ofwhich is incorporated herein by reference, wherein the first number isthe molecular weight of the hydrophilic block segment, PEO, and thesecond number is the molecular weight of the oleophilic block segment,PCL.

TERGITOL® 15-S-7, a C12-C14 secondary alcohol surfactant having an HLBvalue of 12.4, was obtained from the Dow Chemical Corp.

The optical brightener TINOPAL® OB CO was obtained from BASFCorporation.

The porous substrate used in the Examples below was a porous woven 100%polyester fabric Copland Muslin AS931/1 obtained from Copland Industrieshaving a weight of approximately 80-110 g/m².

The carbon black (K) opacifying colorant used as an aqueous dispersionwas Regal 330 (Cabot Corp.) that was hydrophobically surface modified.

SOLSPERSE® 43000, a polyacrylate polymeric dispersant, was obtained fromLubrizol Corp.

The Drapery Compounds were obtained from Eagle Performance Products,where the binder material was a self-crosslinking terpolymer derivedfrom polymerization of acrylonitrile, n-butyl acrylate, and ethylacrylate, and having a glass transition temperature of −10° C.

Measurements:

The mode particle size of the porous particles used in the Examples wasmeasured using a Sysmex FPIA-3000 automated particle size analyzer fromMalvern Instruments. The particle size of the dispersed pigments wasdetermined using light scattering.

The porosity of the porous particles was measured using the mercuryintrusion porosimetry method described earlier

The light-blocking ability of each foamed, opacifying element in theExamples, in transmitted light, was evaluated by measuring itslight-blocking value (LBV) using a custom-built apparatus consisting ofa fiber optic Xenon light source, a computer controlled translationalstage and an optical photometer. The fiber optic was positioned 10 mmabove the surface of the fabric. A photo detector was placed on theother side of the sample element directly under the fiber optic toquantify the amount of light that passed through the sample element. Thelight-blocking value of each sample was calculated by comparing thelight intensity (1) that passed through the sample element to the lightintensity (I₀) that reached the detector when no sample element waspresent, and using the equation:

−log₁₀(I/I₀)

The luminous reflectance (or brightness) of each sample element wasdetermined by first measuring the spectral reflectance in the 400-700 nmwavelength range using a Hunter Labs UltraScan XE colorimeter equippedwith an integrating sphere and a pulsed Xenon light source. A light trapand a standard white tile were used to fix the reflectance range from 0to 100%. The X, Y, and Z tristimulus values of each dry opacifying layerwere also determined and used in conjunction with the CIELab color space(standard D65 illuminant) to calculate specific values for the lightness(L*), red-green character (a*), and yellow-blue character (b*) of eachdry opacifying layer. The Y tristimulus value was used as a measure ofthe luminous reflectance or “brightness” of each sample.

Thermal Colorant Transfer Process:

This process used a thermal donor element comprised of Epson 64″Adhesive Textile Paper onto which desired mirror-image designs orpatterns had been inkjet printed using an Epson F9200 inkjet printer.The mirror-image designs or patterns comprised inks containingsublimable dyes and had been manufactured by Kiian Digital.

Thermal colorant transfer was carried out using a roll-to-roll machinehaving large industrial sublimation calendars. The nip was created by aroll and a belt into which a thermal donor element and superposedopposing external surface of a porous substrate in a foamed, opacifyingelement (having a dry opacifying layer on the internal surface) werebrought into contact. The nip dwell time was 30 seconds at 30 psi (207kPa), and the nip temperature of 190° C. to 205° C., causing sublimationof the sublimation dyes in the colorant donor layer and their binding tothe porous substrate opposing external surface. Transfer quality wasevaluated by visible inspection.

Preparation of Opacifying Colorant Dispersions for Porous Particles:

The opacifying colorant (K), carbon black dispersion was prepared bycombining 10.42 weight % of the dry pigment, SOLSPERSE® 43000 dispersant(20 weight % of the opacifying colorant), and water in a suitablemilling vessel. The particle size of the opacifying colorant pigment wasreduced by milling it using ceramic media until all opacifying colorantparticles were reduced below a diameter of 1 μm as determined by opticalmicroscopy. The dispersion was further diluted with water forincorporation into porous particles. Dv, the volume weighted meandiameter in nanometers, was 101 nm.

Preparation of Porous Particles:

The porous particles used for preparing a foamed, opacifying element forthe Invention Examples is described below.

P1 Porous Particles Containing 0.8 weight % Opacifying Colorant (K) inthe Discrete Pores and 1 weight % Optical Brightener in ContinuousPolymeric Phase CAB

An aqueous phase was made up by dissolving 5 grams of CMC in 240.5 gramsof distilled water and adding to 4.3 grams of the D-K dispersioncontaining 18.6 weight % of carbon black. This aqueous phase wasdispersed in 831.8 grams of an oil phase containing 97.7 grams of CAB, 2grams of PEO-b-PCL and 1 gram of the optical brightener, TINOPAL® OB COin ethyl acetate using a homogenizer. A 975-gram aliquot of theresulting water-in-oil emulsion was dispersed using the Silverson L4Rhomogenizer for two minutes at 1200 RPM, in 1625 grams of a 200 nmolarpH 4 acetate buffer containing 39 grams of NALCO® 1060 colloidal silica,and 9.75 grams of AMAE co-stabilizer followed by homogenization in anorifice homogenizer at 1000 psi (70.4 kg_(f)/cm²) to form awater-in-oil-in-water double emulsion. The ethyl acetate was removedunder reduced pressure at 40° C. after dilution of thewater-in-oil-in-water emulsion with an equal weight of water. Theresulting suspension of solidified porous particles was filtered and theresulting P1 porous particles were washed with water several times,followed by rinsing with a 0.05 weight % solution of TERGITOL® 15-S-7surfactant. The isolated P1 porous particles were then air dried. Theporous particles had a mode particle size of 4.3 μm and a porosity of 40volume %. Typically, the discrete pores contained within the porousparticles prepared according to this procedure had an average diameterof from 150 nm and up to and including 1,500 nm.

Preparation of Foamable Aqueous Composition; Foamed Aqueous Composition;and Foamed, Opacifying Element:

In general, the foamable aqueous composition was made by incorporatingthe porous particles in 48 weight % solids EAGLETEX® C-3018 DraperyCompound. For each foamed aqueous composition, the Drapery compound wasadded to an appropriately sized container. Porous particles weredispersed into the mixture by stirring at 1200 rev/minute with a 50 mmdiameter Cowles blade at ambient temperature for 30-60 minutes. Theresulting dispersion (foamable aqueous composition) was used to preparea foamed aqueous composition under pressure using an Oakes 2M LaboratoryMixer Model 2MBT1A. The resulting foamed aqueous composition, having adensity of from 0.18 g/cm³ to 0.22 g/cm³, was coated onto a surface ofthe porous substrate described above with a coating knife, dried at atemperature of from 120° C. to 160° C. until the moisture content wasless than 2 weight %, and crushed (“densified”) on the porous substratebetween hard rollers under pressure.

INVENTION EXAMPLE 1 Thermal Printing on External Surface

An image was thermally printed on the external surface of a poroussubstrate in a dry opacifying elements in the following manner.

A foamable aqueous composition was prepared with 1400 g of EAGLETEX®C-3018 Drapery Compound and 100 g of a 49 weight % aqueous dispersion ofthe P1 porous particles. This foamable aqueous composition was foamed(aerated) and the resulting foamed aqueous composition was coated ontothe internal surface of the porous substrate described above using acoating knife with a 2.54 mm (0.100 inch) gap in a coating machine at 1m/min and dried at 160° C. The resulting dry foamed composition (dryopacifying layer) in the resulting foamed, opacifying element contained6.71 weight % of the P1 porous particles, 0.0557 weight % of carbonblack (0.136 g/m² of carbon black on a dry weight basis). This foamed,opacifying element exhibited an LBV of 5.8 for the dry opacifying layerweight of 185 g/m², a luminous reflectance value of 52.

A sample of this foamed, opacifying element was thermally printed inaccordance with the procedure for thermal colorant transfer processdescribed above to impart a multi-color floral image to the opposingexternal side of the porous substrate. Good heat transfer printabilitywas evidenced by the fact that 70-80 weight % of the originalcolorant(s) was transferred from the thermal donor element without riskof damaging the foamed, opacifying element. The print quality wasacceptable in as many colors as were available in the thermal donorelement. No delamination of the foamed, opacifying element, and nonoticeable off-gassing from the foamed, opacifying element during thethermal colorant transfer process were observed.

INVENTION EXAMPLE 2 Thermal Printing on Dry Opacifying Layer

Another foamed, opacifying element was prepared according to the presentinvention using the foamable aqueous composition and foamed, opacifyingelement described above for Invention Example 1, except that amulti-color floral image was thermally printed onto the dry opacifyinglayer of the foamed opacifying element. The quality of the thermal printin many colors was acceptable and no delamination or off-gassing wasobserved during the thermal colorant transfer process.

ADDITIONAL INVENTION EXAMPLES

In some other Invention Examples carried out similarly to InventionExample 1, both the opposing external side and the dry opacifying layeron the internal side of the foamed, opacifying element were printedsequentially. In all examples, the quality of the thermally transferredcolor image was acceptable. No delamination or off-gassing was observedfor any of the examples.

In addition, various patterns (images) were similarly thermallytransferred (printed) from suitable thermal donor elements to theopposing external surface of the porous substrate of foamed, opacifyingelements as described above, to provide floral, paisley, or animalpatterns (images), and a red flat patch (image) with excellent results.

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention.

1. A foamed, opacifying element comprising a thermal colorant image, thefoamed, opacifying element further comprising a porous substrate havingan opposing external surface and an internal surface, the internalsurface having a dry foamed composition disposed thereon as a dryopacifying layer, wherein the dry foamed composition comprises: (a) atleast 0.1 weight % and up to and including 40 weight % of porousparticles, each porous particle comprising a continuous polymeric phaseand a first set of discrete pores dispersed within the continuouspolymeric phase, the porous particles having a mode particle size of atleast 2 μm and up to and including 50 μm and a porosity of at least 20volume % and up to and including 70 volume %, and the continuouspolymeric phase having a glass transition temperature greater than 80°C. and comprising a polymer having a viscosity of at least 80centipoises and up to and including 500 centipoises at a shear rate of100 sec⁻¹ in ethyl acetate at a concentration of 20 weight % at 25° C.;(b) at least 10 weight % of an at least partially cured binder material;(c) at least 0.2 weight % of one or more additives comprising asurfactant; (d) less than 5 weight % of water; and (e) at least 0.002weight % of an opacifying colorant different from all of the one or more(c) additives, which opacifying colorant absorbs electromagneticradiation having a wavelength of from 350 nm to 800 nm, all amountsbeing based on the total weight of the dry foamed composition, whereinthe dry opacifying layer has a light blocking value of at least 4 aswell as a luminous reflectance that is greater than 40% as measured bythe Y tristimulus value, and wherein the thermal colorant image isdisposed on the opposing external surface, the dry opacifying layer, orboth the opposing external surface and the dry opacifying layer.
 2. Thefoamed, opacifying element of claim 1, wherein the porous substratecomprises a porous textile web, porous polymer film, porous cellulosicmaterial, porous ceramic material, or porous glass material.
 3. Thefoamed, opacifying element of claim 1, wherein the porous substratecomprises a polyester.
 4. The foamed, opacifying element of claim 1,wherein the dry opacifying layer is the only layer disposed on theporous substrate.
 5. The foamed, opacifying element of claim 1, furthercomprising a dry non-opacifying layer disposed on the dry opacifyinglayer.
 6. The foamed, opacifying element of claim 5, wherein the drynon-opacifying layer comprises a tinting colorant, a flame retardant, anantimicrobial agent, an anti-blocking agent, or a flocking agent.
 7. Thefoamed, opacifying element of claim 1, wherein the dry opacifying layerexhibits a light blocking value of at least
 5. 8. The foamed, opacifyingelement of claim 1, wherein the continuous polymeric phase comprises atleast 70 weight %, based on the total polymer weight in the continuouspolymeric phase, of one or more polymers derived from one or more ofcellulose acetate, cellulose butyrate, cellulose acetate butyrate, andcellulose acetate propionate.
 9. The foamed, opacifying element of claim1, wherein the opacifying colorant is a carbon black that is present inan amount of at least 0.002 weight % and up to and including 1 weight %,based on the total weight of the dry foamed composition.
 10. The foamed,opacifying element of claim 1, wherein the dry foamed compositioncomprises at least 0.5 weight % and up to and including 10 weight % ofthe porous particles, based on the total weight of the dry foamedcomposition, which porous particles have a mode particle size of atleast 3 μm and up to and including 30 μm.
 11. The foamed, opacifyingelement of claim 1, wherein: the dry foamed composition has at least 98%solids; the continuous polymeric phase comprises at least 70 weight %and up to and including 100 weight %, based on the total polymer weightin the continuous polymeric phase, of one or more polymers derived fromone or more of cellulose acetate, cellulose butyrate, cellulose acetatebutyrate, and cellulose acetate propionate; the porous particles arepresent in an amount of at least 0.5 weight % and up to and including 10weight %; the at least partially cured binder material is present in anamount of at least 20 weight % and up to and including 60 weight % andhas a glass transition temperature of less than 25° C.; the one or more(c) additives further comprise an optical brightener in an amount of atleast 3 weight % and up to and including 45 weight %; carbon black ispresent as at least one opacifying colorant in an amount of at least0.002 weight % and up to and including 1 weight %; and the dryopacifying layer has a light blocking value of at least 5, all amountsbased on the total weight of the dry foamed composition.
 12. The foamed,opacifying element of claim 1, wherein the one or more (c) additivesfurther comprise metal flakes that are present within the porousparticles.
 13. The foamed, opacifying element of claim 1, wherein thesurfactant of the one or more (c) additives is a foaming agent and theone or more (c) additives further comprise a foam stabilizing agent. 14.The foamed, opacifying element of claim 1, wherein the one or more (c)additives further comprise a tinting colorant in an amount of least0.0001 weight % and up to and including 3 weight %, based on the totalweight of the dry foamed composition.
 15. The foamed, opacifying elementof claim 1, wherein the one or more (c) additives further comprise anoptical brightener in an amount of at least 0.001 weight % and up to andincluding 0.4 weight %, based on the total weight of the dry foamedcomposition.
 16. The foamed, opacifying element of claim 1, wherein theone or more (c) additives comprise an antimicrobial agent comprisingsilver metal, a silver-containing compound, copper metal, acopper-containing compound, or a mixture of any of these.
 17. Thefoamed, opacifying element of claim 1, wherein the thermal colorantimage comprises a sublimed cyan, yellow, magenta, or black dye, or acombination thereof.
 18. The foamed, opacifying element of claim 1,wherein the thermal colorant image further comprises metal particlesprovided by thermal transfer.
 19. The foamed, opacifying element ofclaim 1, wherein the thermal colorant image is a multi-color image onthe opposing external surface of the porous substrate.
 20. The foamed,opacifying element of claim 1, further comprising a transparentprotective layer over the thermal colorant image.